Investigation on Asphaltene Dispersion Activity of Tetrabutylammonium Carboxylate Ionic Liquids

Abstract

Asphaltene destabilization is still known as one of the main problems of the petroleum industry and imposes many costs on this industry during crude oil production, transportation, and refining. The most important solution to control this problem is using chemical compounds to disperse asphaltene aggregates. Ionic liquids, as an emerging industrial solvent and catalyst, have been used for this purpose in the last two decades. In this work, three ionic liquids having a tetrabutylammonium cation and oleate, stearate, and cinnamate anions were synthesized and used as asphaltene dispersants. The efficiency of the synthesized ionic liquids on the stability of asphaltene aggregates was investigated using cluster size, polydispersity index, zeta potential, and ultraviolet spectroscopy data. It was found that tetrabutylammonium cinnamate and tetrabutylammonium oleate (dispersion indices of 82.5 and 60.2, respectively) have a much higher efficiency than tetrabutylammonium stearate (dispersion index of 20.6). The results of cluster size, polydispersity index, and zeta potential analysis were confirmed by ultraviolet spectroscopy and optical microscopy data. For instance, the mean radius of asphaltene clusters was 2179.8 nm, reduced to 253, 680, and 1402 nm after adding tetrabutylammonium salt of cinnamate, oleate, and stearate, respectively. The same trend was observed in the results of the polydispersity index (0.417, 0.470, and 0.624) and zeta potential analysis (31.4, 1.81, and −0.56). The cinnamate, oleate, and stearate anions have four, one, and no carbon−carbon π bonds, respectively. It seems that the presence of π bonds that can form π−π interactions with π bonds of the asphaltene molecules is an essential factor in asphaltene stabilization by these ionic liquids. In addition, the results showed that the higher the net negative charge of the anion, the greater the ability of the anion to stabilize asphaltene aggregates. This stabilization, which was mainly done through electrostatic interactions between polar groups of asphaltene and the carboxylate anions, was confirmed by zeta potential data.

Ionic Liquid Application To Prevent Asphaltene Precipitation and Deposition during Water-Based EOR Techniques

“…Ionic Liquid Additives. Three different re-synthesized ILs of TBAST, TBAOL, and TBACiN, which have been previously utilized as asphaltene dispersants by Baghersaei et al, 43 were employed to investigate their applicability for preventing or minimizing the asphaltene precipitation in the presence of injected water. To obtain detailed information on synthetic pathways of ILs, refer to the article of Baghersaei et al 43 The synthesized ILs and their structures are illustrated in Table 3.…”

“…Ionic Liquid Characterization. After ILs' re-synthetization based on the study of Baghersaei et al, 43 hydrogen nuclear magnetic resonance ( 1 H-NMR) spectroscopy was performed to confirm their molecular structure, and its results are reported in SI. Since stearic acid, oleic acid, and cinnamic acid were employed to synthesize TBAST, TBAOL, and TBACiN, respectively, the absence of acidic H in the 1 H-NMR spectra confirmed that the synthesis reaction was performed completely.…”

Experimental and Simulation Studies of Imidazolium Chloride Ionic Liquids with Different Alkyl Chain Lengths for Viscosity Reductions in Heavy Crude Oil: The Effect on Asphaltene Dispersion

“…Among them, imidazolium ionic liquid with an alicyclic hydroxybenzene ring had the highest degree of hydrophobicity and demonstrated superior performance in dispersing asphaltenes and achieving significant viscosity reduction. Baghersaei et al [ 23 ] found that ionic liquids primarily stabilize asphaltenes through π–π and electrostatic interactions. The efficiency of asphaltene dispersion is directly related to the net negative anionic charge of the ionic liquid.…”